LabVIEW
Save Sequence Images with a given timing
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Hi Emanuele,
Certainly you can put that indicator outside the loop...I specifically wanted to see if that number grows as you run the program, as indeed it does. (You can also add another indicator outside the loop, wired to the same terminal of "Get Queue Status". Did that make sense?)
It seems that it's taking the consumer loop approximately twice as long to execute as it takes the producer loop, so you're winding up with a bunch of images left in your queue. That's annoying, of course, but it's also something that can be handled. What you need to do now is make sure that your consumer loop doesn't stop executing until all of the images in the queue have been processed.
There are lots of ways to do that. I'll try to put something together as an example for you later today...in the meantime, you can start trying to code it yourself:
- When the extraction loop stops executing, the queue is released. That causes an error to occur in the consumer loop. You can use the error cluster to trap for that error, and take different actions based on whether it has occurred or not. (for instance: no error = dequeue next element. error = extract all remaining elements from queue)
- You know how many items are in the queue because "Get Queue Status" tells you that. So you know how many more images you need to process after the queue is released. As each image is processed, you can decrement that number. When all images have been processed (when you've decremented that number all the way down to 0), stop the loop.
- Look at the help files for the queue functions. Is there a queue function which will return all of the items currently in the queue? If so, that might come in useful, don't you think?
I'm glad you're enjoying LabVIEW. I'm pretty fond of it myself. 
Diane
Hi Emanuele,
Another approach for you to consider:
Don't release the queue until all of the images have been dequeued, processed and saved.
To do that, you'll need some way of knowing whether the producer loop has stopped or not, since no errors will occur in the consumer loop.
Do you know about clusters? Instead of just enqueueing the image, you could enqueue a cluster which contains both the image and the "stop" status of the producer loop. A queue will accept any data type.
I think this is a simpler and better approach than the one I outlined earlier, but you'll need to learn some more new things. Are you up for it?
Diane
Hi Emanuele,
Have a look at this VI, which illustrates the second approach I posted -- not releasing the queue until all of the images have been processed. Do your best to understand it by reading help files, etc., then ask questions.
I still want to see your attempts to implement this yourself, so post whatever you have.
Diane
Hi Emanuele,
Now I really don't understand your question. Could you rephrase it?
Once the data has been enqueued, it remains in the queue until 1) It's dequeued; or 2) the queue reference is released. It has nothing to do with your IMAQ buffers. The two are separate.
Please take the introduction courses as soon as possible. Make the time. I know you say you have a lot of other stuff going on, but make the time. You shouldn't be too busy to learn how to write your own code! You're getting too reliant on me to write your code for you. I realize that's partially my fault since I keep writing code for you...so after this post, I will not write or modify any further VIs for you. After all, this is your project -- not mine. I've given you a lot of help, and you have been very, very good about saying "thank you" (and I appreciate your excellent manners!). Now it's time for you to start learning on your own. You need to understand the code you use, regardless of which one of us wrote it.
I did ask you to try to code up the consumer loop "stop" logic yourself, and post what you tried. I would like to see your effort, so please post it.
I know you have been working very hard on this and I commend your effort. I hope you've learned some things and are excited about LabVIEW!
Diane
